Starting switch for automobiles



April 1931- J. D. SUTHERLAND 1,799,873

STARTING SWITCH FOR AUTOMOBILES Filed May 1. 1929 Patented Apr. 7, 1931 UNITED STATES JOHN DONALD SUTHERLAND, OF

' STARTING SVJITCH Application filed May 1, 1929, Serial No.

This invention refers to switches for controlling the current of the electric motor employed for imparting starting motion to an internal combustion engine, the rotation of which motor causes a pinion to slide into mesh with a toothed wheel or gear on the fiy wheel of the engine.

The objective of the invention is to provide a switch which will function to control the initial speed of the electric motor to set up a slow, smooth engagement of the pinion with the gear on the fly wheel, with the result that much of the usual wear of the teeth of the gear is avoided and consequently the term of usefulness of such gear is extended.

7 In apractical form of the invention the switch is provided with two pairs of contacts, one pair of which first closes the motor circuit through a speed-reducing resistance 90 in the circuit while the other pair subsequently cuts out the resistance and enables the motor to operate to its fullest capacity to impart starting motion to the engine. The

switch is so constructed that an appreciable,

.5 time elapses between the closing of the resistance circuit and of the full-capacity circuit mentioned. Furthermore when the latter circuit is opened the resistance circuit again operates to lower the running speed before the motor circuit is opened.

The accompanying drawings illustrate a practical form of the invention and comprise, Figure 1 a sectional elevation of the switch, and Figure 2 a horizontal section on line II II of Figure 1. Figures 3 and 4. are diagrams illustrating the circuits involved.

The body or casing of the device consists of two parts, the lower part L being hollow and the upper part U, which fits same, consisting of a cover with a central projecting guide or sleeve G.

The base of the lower part is provided with two pairs of contact studs P and P and S and A S, the former being of greater length than the latter. The lower ends of the contact studs are reduced in diameter and threaded and project through the base of the lower part so that nuts may be fitted to each stud which are thus securely fastened in position.

The contact studs S and S, and P also carry ORMOND, VICTORIA, AUSTRALIA FOB AUTOMOBILES 359,674, and in Australia June 13, 1928.

an additional nut each, so that the leads to the starting motor and from the battery may be attached to the studs S and S respectively and the ends of the resistance R to studs P and S.

The resistance R, which consists of a spiral of several turns of a suitable resistance wire, is situated around the outside of the lower part of the casing and is supported at its two ends by the nuts on studs P and S.

The no-load current of the electric starting motor of an automobile is large, (approximately 50 amps. in a 6 volt circuit) so that the resistance employed in this switch need only be small and can therefore consist of a short length of a suitable heavy-gauge resistance wire, which, owing to its stoutness, is self supporting where it is situated in spiral form around the outside of the lower part of the switch and clear of same. The resistance is thus air cooled which is a distinct advantage.

The four contact studs S, S and P, P are completely insulated from the lower part by washers and sleeves of fibre or other suitable insulating material, as illustrated, and the studs S, S and P, P are preferably arranged in axes at right angles to each other.

Within the guide or sleeve G and neatly fitting same are a plunger M and a coil spring 0, and said spring bears at its upper end against a shoulder M on the plunger and at its lower end against an inwardly projecting ledge U at the bottom of the sleeve G of the cover U.

A lateral projection J on the side of the plunger M engages a longitudinal slot J formed in the wall of the guide to prevent rotation of the plunger.

The plunger is formed on its inner end with a sided or square-section central stem M to which are fitted the contact piece X and the contact piece Y,the latter being at about the extremity of the stem and the former a short distance back. The two contact pieces, like the two pairs of studs, are arranged at right angles to each other.

The contact piece Y, while being slightly loose, is retained in position by riveting over the reduced extremity of the stem, and the contact X is formed with a central squared may be used, insulation of the contact loose where they are supported on the stem M of the plunger, they ma rock slightly-in a vertical plane, thereby accommodating themselves to any slight irregularity in the height of the fixed contact studs P, P and S, S.

VJ here it is desirable, the contact pieces may also be insulated from the plunger stem, and thus from the switch casing, by washers and sleeves of fibre or other suitable insulating material in a similar manner. to that adopted in insulating the contact studs. But for the general cases where this switch pieces will not be 'ecessary. V

The contact piece X controlled by a small or lighter coil spring C around the plunger and hearing at its upper end against the shoulderM of the plunger.

The vertical movement of the plunger is limited by the upper side of the contact piece X contacting with the underside of the cover U. a

Electrical connection between the studs S and P is preferably made by a strip of copper Z which is clamped under each thus bridging them.

The device may be fitted to the floor boards of the automobile for foot manipulation, or to any other partfor hand operation, and is supported in position by the two screws? and B as shown.

On the plunger M being depressed, the contact piece X first makes contact with the contact studs P and P, thus completing the initial resistance circuit between the studs S and S through the resistance R, as illustrated in Figure 0. On the plunger being furtherdepressed, the lighter spring G is further compressed and the squared stem of the plunger slides throughthe aperture X in the contact piece X and causes the contact piece Y to make contact with the contact studs S and S in the full-capacity circuit, thus short-circuiting or bridging outthe re sistance R and allowing a direct circuit through the switch as illustrated in Figure 4.

When the depressing force is removed from the plunger, its spring C causes it to return to the original position, first breaking the full-capacity circuit and then the resistance circuit.

Since this switch is designedto permit a slow engagement of the starting pinion with the toothed fly wheel of the automobile, sufiicient time must therefore be allowed in the operation of the switch for this to take place, approximately one second being sufficient; therefore all that is necessary for the eflicient ciently and effectively carry very large electric currents, since the actual area of contact can definitely be measured and ascertained,

in the design; and also owing to the robust construction and ample dimensions of the contact pieces and studs possible in this design of switch, the possibility of damage to such contacts through arcing and burning is ne ligible.

This type of contact is thus superior to any form of spring or wiping contact, for with such contacts the actual area of contact is indefinite, thus rendering them more liable to damage by burning when passing heavy currents.

It will beunderstood that the switch can be adapted to control any type of automobile start'ng motor simply by designing the resistance according to the no-load current taken by the particular motor.

1 claim 1. A starting switch for electric starting motors, comprising a casing; a depressible wring-controlled plunger fitted therein; two

pairs of fixed contactsv of unequal. height mounted in and insulated from the casing and spacedhat regular intervals from one another, one pair. to close a resistance, circuit and'the other pair to close a full-capacity circuit; and a pair of diametrally-arranged Q contact pieces carried by the plunger in superposed relation, the lowerone fixed to and the upper one shdableon the plunger;

.one contact piece adapted to engage the two taller contacts during the initialimovement of the plunger, and the other contact piece adapted to pass between said. taller contacts and engage the two shorter contacts during the subsequent movement of the plunger.

2. A starting switchtor electric starting motors, comprising a casing providedat its top with an upstanding sleeve; a-depressible plunger slidably fitted therein. and ha ing a reduced stem, said plunger and sleeve" forming companion elements, one provided with a guide slot and the other with apin proj ecting thereinto; two pairs of fixed contacts of unequal height mounted in and insulated from the casing and spaced at regular intervals from one another, one pair'to close a resistance circuit and theother pair to close a full-capacity circuit; two diametrally-arranged, superposed contact pieces carried by the plunger stem at its lower end, one attached to said end and the other slidable thereon; one contact piece adapted to engage the two taller contacts during the initial movement or" the plunger, and the other contact piece adapted to pass between said taller contacts and'engage the two shorter contacts during the subsequent movement of the plunger; and spring means fitted in said sleeve between the side wall thereof and the plunger stem and acting on the plunger to hold it elevated.

3. A starting switch according to claim 2, in which the spring means embodies two interfitted springs, one weaker and of smaller diameter than the other, and actin on the sliding contact piece so as to ena le that piece to yield axially along the plunger stem when engagement is made with the two taller contacts.

4. A starting switch according to claim 2, in which the spring means embodies two interfitted springs one weaker and of smaller diameter than the other, and acting on the sliding contact piece so as to enable that piece to yield axially along the plunger stem when engagement is made with the two taller contacts; the reduced lower portion of the plunger stem being of polygonal section, and the upper contact piece having a polygonal aperture through which said stem portion slides; the weaker spring acting directly on said upper contact piece.

In witness whereof I have signed this specification.

JOHN DONALD SUTHERLAND. 

